Plasticization of perhalocarbon polymers



Patented `une 17, 1952 PLASTICIZATION F PERHALOCARBON POLYMERS Herbert J. Passino, Englewood, N. J., assigner to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Application March 25, 1949, Serial No. 83,451

8 Claims.

This invention relates to the plasticization of perhalocarbon polymersf In one of its aspects this invention relates to the production of solid perhalocarbon polymers of modied mechanical and physical characteristics and modified composition. In another aspect this invention relates to the polymerization of trifluorochloroethylene in a continuous manner to produce a normally solid polymer having improved characteristics.

Various unsaturated perhalocarbons may be polymerized under suitable conditions to produce solid polymers of good physical and mechanical stability. In many instances the resulting solid products have physical characteristics such that it is difficult to mold or form products of the desired shape, or have physical characteristics, such as brittleness, which makes their use limited. To alter these physical characteristics of the solid polymers it has been proposed to incorporate plasticizers in the crude polymer product so as to enable easier mechanical handling thereof or to modify their physlcalcharacteristics to the desired extent. These plasticizers may be incorporated with the polymer product by Various means. For, example, the plasticizer may be Worked or kneaded into the solid polymer. Alternatively, the solid plasticmay be polymerized to a finely-divided form and mixed with the plasticizer and then compressed to form a solid-mass. In many instances the plasticizer is diiilcultly miscible with thek polymer product and is not easily dispersed throughout the mass. This is particularly the case when attempting to incorporate a plasticizer into a large mass of polymer, such as that produced in a bomb type reactor.

In producing a solid polymer of trifluorochloroethylene, plasticizers are often employed in combination with the resulting product to modify and improve the physical characteristics thereof. Polymerization of trifluorochloroethylene to a solid polymer is presently effected by a batch-wise process in a bombtype reaction vessel. In the production of the solid polymer, `the monomer is introduced into the-bomb together with a suitable promoter and the temperature of the bomb is usually maintained at about 16 or 17 C. for a period of Aabout seven days. The monomer is converted to a porous plug of the solid polymer in the reaction bomb. The unreacted monomer is included in the interstices of the porous plug and is `removed byheating the plug in the reaction vessel under subatmospheric pressure so that thev vmonomer is evaporated. After the 'unreacted monomer has been evaporated. the plu-g is removed from the reaction bomb and broken into chips or granules. Depending upon its proposed use, often a suitable plasticizer, for example, polymer oil made from the same monomer, is admixed in appropriate amount with the chips or granules of the solid polymer and the mass worked or lineaded into a homogeneous mixture. Relatively small proportions of plasticizer are employed and after suitable Working and kneading the mass is molded or formed into the desired shape by compression, rolling, etc. As previously stated, admixing of the plasticizer with the solid polymer and the Working thereof into the polymer material is diicult and requires an excessive amount of energy and time. It is much to be desired, therefore, to provide a method which could diminish the time and effort re'- quired and Aalso to insure uniform dispersion of the plasticizer in the solid polymer mass.

rIhe Vobject of this invention is to provide a method for incorporating a plasticizer with a solid perhalocarbon polymer.

Another object of this invention'is to provide a method of polymerizing the monomer triiluoro-A chloroethylene toa solid polymer of modified and improved characteristics Still a further object of this invention is to provide a method for obtaining uniform dispersion of a plasticizer ina solid perhalocarbon polymer, such as a solid polymer of trifluorochloroethylene. V

Various other objects and advantages of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.

As herein defined, polymerization refers to polymerization of a single monomer and also to the Vco-polymerization of unlike monomers to produce a polymer of increased molecular weight.

According to this invention, an unsaturated perhalocarbon monomer is polymerized in the presence of a plasticizer under suitable conditions of temperature, pressure, residence time and pro-l moting agent to produce a normally Vsolid perhalocarbon polymer having modified and iml proved chemical and physical characteristics as compared to the polymer produced Without the presence of the plasticizer. Thesolid polymers produced by the process of this invention Yare those which retain their shape but are capable of being deformed by heating, compression. etc. The polymers produced are also characterized 'by the fact that their physical and chemical properties are modified by .the vpresence of the plasticizez; during polymerization, such that theresulting solid polymer may have any one of the following modied characteristics, namely. hardness, resilience, softening point, brittleness, translucency, plasticity and stability, as compared with the normal product produced Without the presence of the plasticizer under otherwise comparable or substantially identical conditions of polymerization. The polymerization process of this invention may be effected in either a batch-Wise or continuous manner. The monomer is usually admixed with the plasticizer and introduced into a suitable polymerization zone under the appropriate conditions of polymerization in the liquid phase A suitable diluent or heat dissipating. medium may also be admixed with the monomer without departing from the scope of this invention. The resulting product is separated from the reaction mixture by any suitable method, such as by settling and decantation, filtering, centrifuging, and evaporation. The method of separation and recovery of the solid polymer will depend upon various factors, such as the extent of polymerization, the amount of diluent, if any, employed, and the design and shape of the apparatus.

The present invention contemplates the use of various perhalocarbon monomers for producing the solid polymer. These perhalocarbon monomers comprise triuorochloroethylene, perfluorobutadiene, perfluoropropene, peruorostyrene, peruorocyclobutene, periluorocyclobutadiene, and tetrafluoroethylene. As previously mentioned, the invention applies particularly to the polymerization of triuorochloroethylene to produce a solid polymer. It also applies to the co-polymerization of various monomers such as, for example, the co-polymerization of triuorochloroethylene and tetrauoroethylene, the co-polymerization of perfluorobutadiene and perfluorostyrene, and the co-polymerization of peruoropropene and triuorochloroethylene to produce solid polymers.

The plasticizer employed in the present invention is one which is liquid under the operating conditions and which imparts to the resulting solid polymer modified and improved characteristics. Suitable plasticizers comprise the oils, greases and waxes obtained by the polymerization of trifluorochloroethylene, acetone, chloroform, carbon tetrachloride, methylene chloride, dichloroethylene, trichloroethylene, tetrachloroethylene, 1,1,2 trifluorotrichloroethane 1,2-, 1,1diuorotetrachloroethane, perluoroethers, perluoroketones, perchloroethers, perchloroketones and various other halogenated hydrocarbons. The plasticizer must be at least partially miscible and substantially non-reactive with the polymer product. The weight ratio of monomer to plasticizer employed is usually in the range of about 50:1 to about 1:1, preferably between about :1 to about 10:1. The amount of plasticizer employed will depend in general upon the desired extent of modification to be effected on the resulting solid polymer, the exact ratio being Within the determination of one skilled in the art for each particular set of reaction conditions employed and product desired.

Since the present invention has particular application to the plasticization of solid polymers of triiluorochloroethylene, although not limited thereto, suitable and preferred plasticizers. for this polymer are the oils, greases and waxes of the monomer itself. These oils, greases and waxes are produced at higher temperatures than employed for the production of the solid polymer and in the presence of a chain transfer reactant, such as chloroform. For a more complete discussion of the manner of producing solid polymers and oils of triuorochloroethylene, reference may be had to applications Serial Nos. 14,797 filed March 13, 1948, by William T. Miller, now Patent No. 2,579,437; 20,612 led April 13, 1948, by John S. Rearck and 61,082 led November 19, 1928, by Albert L. Dittman, John M. Wrightson and Herbert J. Passino. These applications disclose in general the various operating conditions, apparatus and characteristics of the product produced by the polymerization of trifluorochloroethylene.

The drawing is a diagrammatic illustration of an arrangement of apparatus in elevation for a continuous process for the production of a normally solid polymer of modified and improved physical and chemical characteristics from the monomer trifluorochloroethylene. The starting material trifluorochloroethylene may be prepared by dechlorinating Freon 113, triuorotrichloroethane, in the presence of powdered zinc. According to the drawing, triuorochloroethylene together with any impurities accompanying the monomer is introduced into a fractional distillation column 4 through conduit 3. Recycled monomer is introduced into the lower portion of column 4 through conduit 35. In fractionator 4, trii'luorochloroethylene is recovered as an overhead fraction in substantially pure form. Liquid bottoms are maintained at the desired temperature of about 86 C. at atmospheric pressure by a conventional heating or cooling element 6. Undesirable high boiling components or impurities accompanying the trifluorochloroethylene are withdrawn from fractionator 4 through conduit 'I for disposal. rI'hese undesirable components comprise alcohol and acidic by-products. Vaporous trifluorochloroethylene is removed from the upper portion of fractionator 4 and passed through conduit 8 and condenser 9 to accumulator Il. At least a portion of the trifluorochloroethylene is condensed by condenser 9 which is maintained at a temperature of about -28 C. for atmospheric pressure operations. Condensate is returned from accumulator l l through a conduit l2 to the upper portion of fractionator 4 as reflux. Alternatively or additionally to refluxing with condensate in conduit l2, internal cooling means (not shown) may be positioned Within the upper portion of fractionator 4 for creating an internal reflux.

If only that much of the vapors in conduit 8 are condensed so as to provide reflux to fractionator 4, the remaining vapors are removed from accumulator H and are passed through conduits I4 and I6 to a scrubber Il to remove acidic material from the monomer stream. In treater I1 the monomer stream is contacted with a caustic solution of sodium or potassium hydroxide. This treatment in scrubber I1 may also comprise contact with suitable sorbents, such as silica-gel, phosphoric pentoxide and activated carbon, for removal of traces of contaminants, such as alcohol. Scrubber I1 is used in order to obtain a monomer of high purity which is desirable for the polymerization of triuorochloroethylene to a solid polymer of good physical and chemical properties.

In case it is desired to treat the monomer in the liquid phase, liquid monomer is withdrawn fromV accumulator Il and passed through conduits I3 and I6 to scrubber l1 for liquid-liquid contact with a caustic solution and/or sorbents. When this modification is employed, condenser 9 is operated so as to condense substantially all ofthe effluentI in conduit 8. Y

Liquid monomer is withdrawn from scrubber I1 and passedA through conduit I8 to a. mixing tank I9. In the' event the monomer is treated in scrubber I1 in the vapor phase, a condenser (not shown)` is provided on conduit I8 to condense the vapors. A plasticizer in thev appropriate quantity is introduced into mixing tank` I9 where it is thoroughly dispersed in the monomer. Preferably, the plasticizer is a polymer oil of triiluorochloroethylene.- This oil isproduced at about 75- to 100 C. in the presence of a small amount of chloroform as a chain transfer solvent. The crude oil removed from the polymerization zone is fractionated into a desired fraction boiling between `about 1 0() and 250 C. at 1-2 mm. of'mercury. fraction is then fluorinated with chlorine trifluoride or cobaltic fluoride to render it stable and substantially non-reactive. VThe quantity of poly trifluorochloroethylene oil introduced into mixing tank` I9 is about 0.1 part by weight per part by weight of monomer; the amount of plasticizer.- however, 'will dependl on various factors as previously discussed.

From mixing tank I9, the purified liquid monomer including the plasticizer in appropriate quantity is passed through conduit 2I to a polymerization reactor 22. Water or other diluent may be introduced into reactor 22 through conduit 24r to aid in the removal of the heat of polymerization as hereinafter described. The introduction of water and/or monomer maybe intermittent or continuous. A suitable promoter, such as sodium perborate, is also introduced in measured quantities by means of conduits 26 and 24. The temperature ofreaction employed may be about C. to about 50 C. but higher or lower temperatures may be used without departing from the scope of this invention. In order to maintain the monomer in the liquid phase a pressure of about 100 pounds per square inch gage or higher is maintained in Areactor 22. Liquid monomer and water are vigorously and intimately admixed in reactor 22 by means of a conventional stirrer 23. i

If water is used as a diluent, the quantity of water employed for removal and absorption* of the heat of polymerization in reactor 22 is between about 1 and about 3 times that of the monomer. A preferred amount of sodium perborate is between about'0.5 and about 5 weight per cent based on the monomer` in reactor 22. The average residence time of the monomer in order to produce solid polymer is-between about 5 and about hours. The solid polymer containing the plasticizer forms as a white powder and is removed as a slurry with water and unreacted monomer through conduit 21.

The slurry of solid polymer is passed from 'reactor 22 through conduits 21 and 28 to a `stripping unit 3l in which unrcaeted monomer is stripped from the slurry containing polymer by increasing the temperature and/or decreasing the pressure of the system. Vaporied monomer is withdrawn overhead from stripper 3IV throughV conduit 32 and may be recycled to reactor 22, or all or' a portion thereof may be passed Athrough conduit 35 to fractionator 4. Numeral'33 ini dicates heating coils for stripping purposes. When passing the monomer from stripper 3l to fractionator 4, a condenser is usually positoned on conduit 35 to condense the monomer'A stream prior to' introduction into fractionator 4..

A slurry of polymer and Water substantially free from monomer is withdrawn from stripper 3Ithrough conduit 34 and is passed to. asepa.-`

reactor 22through conduits 21,' 29. and 34directlyto separator 36 by proper adjustment of the valves on conduits 28 and 29.v When the stripping step is eliminated the polymer willV be heavier thanv water and will settle to the bottom of separator 36, from where it is removed and recovered.

, Separated polymer which may or may not convtain monomer is passed from separator 36 through` conduit 39 to drier 4I. In drier 4I water and/or monomer are evaporated and passed through condu'it 43 for return through conduits 45, 35 and 32 to reactor 22, or to fractionator 4 through conduits 45 and 35. If desired, the vapors removed from drier 4I may be vented to the atmosphere; this usually being thecase when the stripping step is employed. On the other hand, when the stripping step is not used thevapor's in conduit 45 willcontain an appreciable amount of monomer and it is preferred under such circum stances to recycle the monomer to reactor 22 or fractionator 4. Driedlpolym'er is removed from drieif4l through conduit 42 as a product of the process.

In a modification of the present process-in which the 'solid polymer may contain excess amounts of promoter, such as sodium borate, hav-V ing adverse affects on the polymer product, the separated solid polymer is passed from conduit 39 through conduit 43 to an extractor 44;V Ih extractor 44 the polymer ,is washed with an aqueous solution, preferably an aqueoussolution of alcohol to dissolve the inorganic peroxides contained in the polymer. Thesolid'polymer. is allowed to settle in extractor 44 land, may be passed through conduit 4I; to 'drier' 4I, if desired.v The aqueous solution contain-ing the extracted peroxides or other impurities is removed from ex'- tractor 44 through conduit 53 and passed to a stripper 54. comprising -an aqueous solution of alcohol is obtained and returned .to extractor 44 through conduit 52. A bottoms fraction comprisingwater and impurities, such as inorganic peroxide, is

removed Vfrom stripper 54 through conduit v51.'.

Since the inorganic peroxide may be usefulas a promoter for the polymerization reaction, the streamin conduit 51 may' be returned to reactor 22 by means not shown.. Element 56 is a'heating coil or reboiler for heating stripper 54 to a sufiiciently high temperature to vaporize the extracting agent. Methyl alcoholmay be admixed in about a 1:1 weight ratio with water for use in extractor 44. i

In the event it is undesirable to pass the treated polymer from extractor 44 to drier 4I because of the presence of alcohol which may contaminate the monomer, the extracted polymer may be passed through conduit 41 to drier 48. In drier In stripper 54 anV overhead fraction 48 the alcohol and water contained in the solid polymer are evaporated by regulation of the temperature and/or pressure therein in the conventional manner. The vaporized components are removed from drier 48 through conduit 5I. Dried polymer containing the plasticizer is removed from drier 48 through conduit 49 as a product of the process.

The solid polymer recovered at 42' or 49 contains the plasticizer as a homogeneous mixture. The polymer product may be subjected to further treatment such as Dyrolysis, iiuorination, chlorination, etc. without departing from the scope of this invention. Various modifications and alterations of the arrangement of the equipment may become apparent to those skilled in the art. Certain pieces of apparatus and auxiliary equipment, such as liquid level controls, flow controls, temperature and pressure controls, valves, pumps, coolers or condensers. heaters and storage vessels have been omitted from the drawing as a matter of convenience and clarity.

With the diluent, the reactor is cooled or heated by controlling the quantity and temperature of the fresh and/or recycled diluent introduced into the reactor. Because of the high heat transfer rate of the diluent, such as water, temperature control of the reactor is relatively simple and accurate without wide variations in temperature occurring. Control of the reactor temperature is usually maintained by means of a cooler (not shown) positioned on recycle conduit 38, which removes the heat of polymerization absorbed by the diluent. The temperature of the reactor may be maintained substantially constant at the desired level without the use of a diluent, if desired, by indirect heat transfer with the reactor, such as by immersing the reactor in a liquid bath or by using coils positioned within the reactor.

I claim:

1. The method of plasticizing a solid polymer of triuorochloroethylene which comprises polymerizing triuorochloroethylene at a temperature between about C. and about 50 C. to produce a homopolymer of triuorochloroethylene in the presence of polytrifluorochloroethylene oil present in a weight ratio of monomer to oil of about 50:1 to about 1:1.

2. A continuous process for polymerizing triiiuorochloroethylene to a normally solid polymer of improved chemical and physical characteristics which comprises introducing triuorochloroethylene, a polytriuorochloroethylene oil as a plasticizer, and water into a reaction zone in the presence of an inorganic peroxide as a promoter, maintaining the reactor at a temperature between about 10 and about 50 C. and under suiiicient pressure to maintain the monomer in the liquid phase, vigorously agitating the mixture of monomer, plasticizer, and water, maintaining an average residence time of monomer in said reactor such that a normally Vsolid homopolymer of trifiuorochloroethylene is produced, withdrawing a slurry of monomer, solid polymer and water from said reaction zone, stripping the monomer from said slurry and returning stripped monomer to said reaction zone, separating solid polymer from water from said reaction zone and returning the water thus separated to said reaction zone, drying the polymer, and recovering dried plasticized polymer as a product of the process.

3. A process for polymerizing triiluorochloroethylene to a normally solid polymer of improved chemical and physical characteristics which comprises introducing triuorochloroethylene, a polytrifiuorochloroethylene oil as a plasticizer, and water into a reaction zone in the presence of an inorganic peroxide as a promoter, maintaining the reactor under suiicient pressure to maintain the monomer in the liquid phase at the temperature employed, vigorously agitating the mixture of monomer, plasticizer, and water, maintaining an average residence time of monomer in said reactor such that a normally solid homopolymer of trifluorochloroethylene is produced, withdrawing a slurry of monomer, solid polymer and water from said reaction zone, separating solid polymer from water from said reaction zone, drying the polymer, and recovering dried plasticized polymer as a product of the process.

4. 'Ihe method for plasticizing a solid polymer of trifluorochloroethylene which comprises polymerizing trifluorochloroethylene in the presence of polytriuorochloroethylene which is liquid under the polymerization conditions under conditions to produce a normally solid homopolymer of trifiuorochloroethylene containing plasticizer.

5. The method of plasticizing a solid polymer of triiluorochloroethylene which comprises polymerizing the single monomer triuorochloroethylene to produce a homopolymer thereof in the presence of polytrifluorochloroethylene oil present in a weight ratio of monomer to oil of about 10.

6. A process for plasticizing a normally solid perhalocarbon polymer which comprises admixing polytriiiuorochloroethylene of lower molecular weight than said normally solid halogenated polymer to be plasticized and a material selected from the group consisting of triiluorochloroethylene and trifiuorochloroethylene and another halogenated olefin and polymerizing the aforesaid material in the presence of said polytriuorochloroethylene which is a liquid under the conditions of polymerization under conditions such that a solid polymer of modified mechanical and physical characteristics is produced.

7. 'I'he process of claim 6 in which triuorochloroethylene is copolymerized with tetraiiuoroethylene.

8. The process of claim 6 in which trifluorochloroethylene is copolymerized with periiuoropropene.

HERBERT J. PASSINO.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,230,654 Plunkett Feb. 4, 1941 2,393,967 Brubaker Feb. 5, 1946 2,394,243 Joyce Feb. 5, 1946 2,398,926 Dorough Apr. 23, 1946 2,456,255 Coffman et al Dec. 14, 1948 2,513,312 Hanford July 4, 1950 OTHER REFERENCES Hooker Chemicals Advertisement, ChemicalA 8: Engineering News, Dec. 25, 1943 vol. 21, No. 4, page 2084.

Miller et al., Ind. and Eng. Chem., vol. 39, No. 3, pp. 333 and 337. 

6. A PROCESS FOR PLASTICIZING A NORMALLY SOLID PERHALOCARBON POLYMER WHICH COMPRISES ADMIXING POLYTRIFLUOROCHLOROETHYLENE OF LOWER MOLECULAR WEIGHT THAN SAID MORMALLY SOLID HALOGENATED POLYMER TO BE PLASTICIZED AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF TRIFLUOROCHLOROETHYLENE AND TRIFLUOROCHLOROETHYLENE AND ANOTHER HALOGENATED OLEFIN AND POLYMERIZING THE AFORESAID MATERIAL IN THE PRESENCE OF SAID POLYTRIFLUOROCHLOROETHYLENE WHICH IS A LIQUID UNDER THE CONDITIONS OF POLYMERIZATION UNDER CONDITIONS SUCH THAT A SOLID POLYMER OF MODIFIED MECHANICAL AND PHYSICAL CHARACTERISTICS IS PRODUCED. 